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IN APRIL, the residents of Delhi went gone through another two-week experiment in the rationing of private car movement according to the last digit of their number plates — odd numbers allowed to move on odd dates and even numbers on even dates. Over a period of six months, three to four experts raised the same issues every day, had the same disagreements, and the media repeated them faithfully. But the PM 2.5 debate refused to settle.

The government deemed the experiment a “success” but no one knows what data had been used to come to this conclusion. Even experts didn’t agree on some of the basic issues: Did pollution decrease? Did traffic improve? Which vehicles cause the most pollution? What are the other sources of pollution besides vehicles?

It is not surprising that spokespersons from different organisations produced different numbers for the same phenomenon: In the absence of real data, all of them had to make assumptions on what is happening on the ground and run their own models. Consequently, the public and the government really did not have a clue as to whom to believe, when and why.

We are placed in this predicament because we really do not have enough reliable data in Delhi for calculations regarding all sources of pollution and its effects.

Consider the following:

Anyone who attempts to estimate vehicular pollution in Delhi has to rely on assumptions. This is because no one has ever taken a random sampling of various vehicles and measured their emissions while they are on road. So no one knows what CNG buses, taxis or three-wheelers of different ages actually emit while operating at different speeds. All of us are forced to estimate these numbers from new vehicle test results or data from abroad. For example, every chemist knows that NOx is not produced by the fuel used but by Nitrogen and Oxygen in air combining when any fuel burns in an engine. The amount produced increases with increase in temperature of combustion. Diesel engines produce more NOx than petrol engines because diesel burns at a higher temperature than petrol. But, CNG also burns at a much higher temperature than petrol and therefore it is possible that all CNG vehicles produce more NOx, creating more Ozone than petrol cars. But there is no discussion on this issue.

No one knows how many cars and motorcycles operate in Delhi; official statistics appear to be much higher than actual figures. Almost 15 years ago, R. A. Mashelkar, as chair of the expert committee on auto fuel policy, had attempted to estimate the number of vehicles in Delhi. His study informed us that actual number of operating vehicles was about 60 to 65 per cent of the registered numbers; the transport department ignored the findings. The numbers made sense to me because over the past 25 years, I have sent four vehicles to the junkyard but still possess all the registration certificates. It appears that most people never have a vehicle deregistered. Two years ago, we did surveys in Delhi, Rajkot and Vishakhapatnam to understand whether the Mashelkar Committee report was still usable. Our results confirmed that the number of cars and motorcycles actually on the roads of Delhi might be only about 50 to 55 per cent of those registered.

The above two examples suggest that policy makers are announcing “drastic” measures to control pollution without real facts. For example, our survey also showed that cars over 10 years old comprise only seven per cent of the fleet and those over 15 years are only one per cent. These old cars are also driven much less than the younger ones. But, we still believe that banning old cars will make a substantial difference in Delhi’s pollution levels.

The lack of reliable data regarding pollution does not apply to motor vehicles alone. We have similar issues in estimating the contribution of gensets, bulldozers and construction equipment. Luckily, we do have somewhat reliable estimates for PM 2.5 emissions as the chemical analysis of particles does not depend on counting anything. Different broad categories of combustion have different signature profiles of trace elements and carbon types and these can be used for identifying broad sources as engines, wood burning, coal burning, dust etc. These analyses suggest that total contribution of traffic may be in the range of 20 to 25 per cent of PM 2.5 in the air. But they cannot give us details of sources within each category.

Since we have so many sources of emissions, no drastic measure can come to our rescue. We must get a much better idea of how to plan short-term and long-term solutions for many sectors. For this, it is necessary to get studies done for better data on the situation in Delhi.

For a start we must have on-road, real-driving emissions tests done using portable emission measurement systems. If we find that CNG vehicles are not as clean as we thought them to be, then this would be the right time to shift to emission-based standards and jettison the idea of prescribing fuels. There is general agreement around the world that prescribing specific fuels and technologies is harmful as it discourages innovation and promotes monopolies. On the other hand, when we prescribe performance norms, industries compete to lower prices and produce alternative solutions for the same performance.

The best decision taken yet is the move to introduce Bharat VI emission and fuel norms as soon as possible. This will be a major improvement over the present situation. In the meantime, we must start working more seriously on detailed cost-effective studies to ensure various options are available to draw up time-bound programmes with measurable milestones. At this juncture, it is veryimportant to remember M.K. Gandhi’s time-honoured advice: “Action in the absence of knowledge can be dangerous and worse than no action at all”.The writer is distinguished professor, Shiv Nadar University, and guest professor, Transportation Research and Injury Prevention Programme.